This invention pertains to the field of control systems for scale model railroad layouts, and specifically to improvements in locomotive decoder (receiver) device interface connections and mode-conversion capabilities.
The advent of Command Control technologies has led to increased enjoyment and capabilities for model railroaders and their operations of model railroad layouts. Since the early Carrier Control systems of the 1970""s and up to the latest Digital Command Control technologies, the key capability of all the technologies is the same. This is the ability to control multiple independently addressed locomotives in the same electrical section of model railroad tracks. All the technologies that communicate these addressed commands to a particular receiver, or decoder, in the locomotive by electrical conduction via the rails employ some variant of encoded time-varying voltage waveforms, and are termed Command Control systems. Additionally, some 1990""s prior art Command Control systems have been developed that control decoders via a Radio Frequency link or an Infra Red data link, with energy supplied via the track or batteries, and these variants can be also considered to behave in a similar manner and scope to the systems discussed herein. As technology and miniaturization have improved, the encoding methods, features and capabilities have been upgraded, but the net effect is still fundamentally that of allowing multiple simultaneous train control capability in at least a single track-section. This is a capability that no earlier xe2x80x9cconventionalxe2x80x9d AC or DC power-pack systems possessed and is why these older single-control per track systems have been surpassed by Command Control methods.
The earliest GE xe2x80x9cAstracxe2x80x9d system was one of the first xe2x80x9cfrequency modulatedxe2x80x9d waveform train Command Control systems, along with the methods employed by Lahti in U.S. Pat. No. 4,341,982. In the early 1980""s the Hornby xe2x80x9cZero-Onexe2x80x9d system, as taught by Palmer in U.S. Pat. No. 4,335,381, provided one of the first examples of a modem Digital Command Control, or DCC, system with digital command encoding methods that are direct precursors of the latest message-based Digital Command Control art. Additionally, the Marklin xe2x80x9cAC Digitalxe2x80x9d or Trinary DCC system was also introduced in the mid-1980""s, and is taught by Hanschke in U.S. Pat. No. 4,572,996.
The freedom to operate multiple receiver, or decoder, equipped locomotives then raised a further novel question of interchange of and coupling of different technology locomotives on and between layouts equipped with the exciting technologies of, Command Control, Digital Command Control or Carrier Control and other conventional layouts and locomotives without these new capabilities. These different modes of operations are not inherently compatible.
One of the earliest widely known publications to identify this equipment interchange and compatibility issue was by Craig Kosinski in a March 1983 Railroad Model Craftsman magazine article. In this article Kosinski clearly identifies the problem of running the xe2x80x9cnewxe2x80x9d Carrier Control (also often termed Command Control) technology steam locomotives on a conventional DC controlled layout, with other DC controlled locomotives or trains. Kosinski proposes an obvious and simple functional solution to the problem. Kosinski teaches the addition of a double-pole double-throw (two configurations) xe2x80x9cchangeoverxe2x80x9d style switch to bypass the receiver, or decoder, and allow the locomotive motor to be fed directly from the track power or energy source. As Kosinski states, this allows xe2x80x9cmaking the control system optionalxe2x80x9d, and neatly solves the interchange dilemma between different control technology locomotives and layouts. With the decoder bypassed, the motor allows the locomotive to act in tandem and to be safely coupled with other DC motor locomotives, in a wholly compatible manner. The extension of this bypass switch method to be used with locomotives from DCC systems such as xe2x80x9cZero-Onexe2x80x9d is also noted, along with cautions for incorrect switch settings. Note that in this configuration the two motor leads are switched, each by an individual switch pole, and there are two current carrying positions for each motor lead switch pole. All six leads of the switch are involved in power (or energy) conduction, and the locomotive motor selectively receives energy from either the energized decoder or directly from the tracks, but not both the decoder and the track energy source simultaneously.
The problem of interchange between DCC decoder equipped locomotives onto DC systems, and also the reversed situation of operating DC locomotives on DCC systems, was also addressed by systems based on the public domain NMRA DCC Standards, introduced in the early 1990""s, and based on the earlier Marklin xe2x80x9cDC Digitalxe2x80x9d system. In particular, the NMRA DCC technology allowed for automatic, or selectable, Power Mode-conversion options that allowed the decoder to detect that it was connected to a conventional track energy supply, or other control method, rather than a compatible DCC encoded control system. Accordingly when the decoder or receiver detects the tracks being driven by a conventional power system it modulates the H-bridge motor drive circuit so as to supply the input power directly to the motor. The speed of the motor is then mainly controlled by the amount of conventional voltage supplied and is further usefully modified by decoder actions. The NMRA prior art uses the term xe2x80x9cmode-conversionxe2x80x9d to describe the action of a decoder, or other control device, that detects a change of the nature of the track energy supply it is connected to then allows a change of control action or strategy based on the new type of energy supply.
While in this non-DCC mode-conversion state, the 1990""s prior art decoders continue to enjoy useful DCC benefits, such as; Digitrax FX lighting effects like xe2x80x9cMars lightsxe2x80x9d enabled while in conventional mode by NMRA Configuration Variable CV13, the simulated Braking and Acceleration momentum effects specified by NMRA Configuration Variables CV04 and CV03 respectively, over-temperature and overcurrent protection logic and many other capabilities such as decoder data feedback or transponding.
Since all decoders employ an input-rectifying bridge circuit (to allow locomotive placement or connection to the track in either direction) the motor H-bridge power 95 supplied as the output of this input-rectifying bridge circuit removes the direction control information implicit in the track conventional DC polarity control. The decoder control logic additionally now has to sense the DC polarity of the tracks prior to the input-rectifying bridge circuit and then appropriately modulate the H-bridge motor drive circuit to faithfully reproduce the intended motor and movement direction. This automated mode-conversion or power pass-through and direction determination was also extended to conventional AC control systems. In the 1990""s commercial DCC decoders were produced that could sense the higher voltage direction reversing pulse used by Marklin conventional AC power packs to change direction, or the power cycling sequence used by Lionel ZW type of AC controlled locomotives to discriminate the correct direction commanded. In some decoders the programming or switch-configuring of decoder address to 00 (not a unique control address) forces the decoder to remain in the conventional power or energy pass-through control state.
The converse state of operating a DC locomotive on a DCC equipped track was also made possible with the Analog mode xe2x80x9czero-bit stretchingxe2x80x9d allowed by the NMRA DCC Standard.
The goal of all these products, efforts and technologies employed all through the 1990""s was to allow decoder equipped locomotives to operate with compatibility on conventional control systems (and vice-versa) and allow trains and multiple-unit locomotive xe2x80x9clash-upsxe2x80x9d, or consists, to be freely formed with a mixture of different technology locomotives.
The ubiquitous presence in decoders of the input-rectifying bridge circuit and the H-bridge motor drive circuits cause a problem, in that the decoder equipped locomotives necessarily will run at a slower speed than unconverted conventional locomotives when on a conventional layout. Here the decoder-equipped locomotives will not accurately or compatibly respond to the desired conventional mode speeds commanded to other conventional locomotives by the conventional track energy supply. This inaccurate mode-converted response of decoder equipped locomotives to conventional control voltages means that it is problematic to physically consist, or couple, conventional locomotives to decoder equipped locomotives that do not employ voltage accurate mode-conversion.
This is due to the fact that the input-rectifying bridge circuit has significant semiconductor diode forward conduction voltage drops of about 2xc3x970.7 Volts=1.4 Volts. More significantly, the typical modern Field Effect Transistors (MOSFETs) employed in the motor H-bridge drive circuits need several volts of control gate input voltage to allow significant motor current conduction. Also, the control logic, or even microprocessor controller CPU, typically needs 2 or more volts to become functional. This means that a decoder that mode-converts on DC track will not even start to allow motor movement before the DC voltage is about 3 or 4 volts or more, and then the motor running voltage will be several volts less than a comparable motor in a conventional non-decoder locomotive. Clearly a decoder equipped locomotive can be run on a conventional layout, but a consist or multiple unit xe2x80x9clash-upxe2x80x9d or tandem operation cooperating with conventional locomotives is problematic. This difference of voltage accuracy in decoders responding to conventional control voltages has been widely known since the early 1990""s. Of course, when running on a conventional layout, the decoder equipped locomotives can offer no additional independent multiple-train control capability beyond that created by the power switching and track xe2x80x9cblock controlxe2x80x9d employed on those conventional layouts.
The NMRA adopted a Recommended Practice (RP) in the mid- 1990""s with a switch-plug arrangement as NMRA Recommended Practice RP-9.1.1, and this is often used to address this speed accuracy or voltage disparity problem, as well as make a decoder convenient to install and uninstall. This RP allows a multi-pin plug arrangement installed in the locomotive to select the bypass xe2x80x9cconventionalxe2x80x9d mode using a xe2x80x9cshorting plugxe2x80x9d to connect the motor to receive energy only from the track pickups, or be mutually exclusively switched to a decoder plug to allow the motor to receive energy only from the decoder. This switching is specifically arranged such that it is not possible for the motor to be connected to, or receive energy from, both sources simultaneously, even when the decoder resides inside the locomotive. This arrangement has provided for and has been commonly used for many years in the 1990""s by model railroad clubs and individuals with HO scale locomotives to allow for switching back a decoder equipped locomotive to run properly and accurately on a conventional layout. This is also a method that is directly related to and clearly anticipated by Kosinski, since a motor double-pole changeover switch arrangement is created with two different and distinct switch states (two configurations) that both carry the load current, and this intentionally allows xe2x80x9cmaking the control system optionalxe2x80x9d for mixed locomotive technology operations.
In 1995 Digitrax Inc. introduced the DH84 DCC decoder with an integral 9-pin JST connector and a matching inexpensive harness system and shorting plug arrangement that was designed to allow the relatively expensive decoder to be shared amongst many harnessed locomotives. The consumers appreciated the cost savings, and could typically use a ratio of four or ten harnessed locomotives to one decoder, and this allowed large fleets of locomotives to selectively enjoy the benefit of DCC operations at an affordable cost. This greatly reduced resistance to conversions of layouts to DCC technology. The locomotives without a decoder plugged in would have a matching shorting xe2x80x9cjumperxe2x80x9d plug installed that would allow accurate and compatible motor operation on conventional DC layouts or even operation on zero-stretched DCC layouts. Model railroad clubs frequently use this capability since they often partition the layout into DCC and conventional DC controlled areas to satisfy members"" preferences. This technique is analogous and functionally equivalent to the NMRA RP-9.1.1 locomotive socket method, but was intended for locomotives that were not originally manufactured with an integral NMRA decoder socket. It is thus, also considered a logical derivative of Kosinski, and in fact was so popular that the NMRA incorporated the 9-pin JST variation into a revision of RP-9.1.1 several years after the DH84 was introduced. Interestingly, many users would employ the DC shorting xe2x80x9cjumperxe2x80x9d plug for DC layout operations to get best voltage accuracy, even though the DH84 itself embodied automatic detection and mode-conversion for DC layout operations.
The November 2000 Graf U.S. Pat. No. 6,320,346 covers this same ground and capability as taught by the just outlined and widely documented prior art. Unfortunately, Graf does not disclose the full extent and body of prior knowledge, techniques and efforts widely known in the industry as relevant to mode-conversion or switching methods. In particular, Graf only shows the use of a double-pole double-throw (two configurations) or xe2x80x9cchangeoverxe2x80x9d style switch (or equivalent relay or contactor) to select the source of the energy supplied to the motor.
The switch arrangement shown and claimed only allows motor energy to be provided selectively and mutually exclusively by either a first decoder connected configuration or by a second track connected configuration. All six terminals of the changeover switch are used to carry currents. This technique is clearly anticipated by Kosinski and NMRA RP-9.1.1 The lack of research into, or knowledge of, the prior art leaves the Graf method without a clear and reasoned distinction over demonstrated prior art, and the obviousness and lack of novelty raises doubts as to the validity of the Graf Patent.
Interestingly the methods taught by Kosinski and RP-9.1.1 and used by Graf are not the most optimal, simplest or most cost-effective methods to allow accurate mode-conversion of decoder equipped locomotives.
Additionally, if the changeover switch is implemented with the obvious electrical equivalent of a relay switch or electrical contactor, as suggested by Graf, there is a significant problem when attempting to Service Mode Program using the commonly required NMRA RP-9.2.3 DCC programming method to configure Configuration Variables (CVs) in the DCC decoder. A typical HO or N scale locomotive motor presents about a 10 to 15 ohm impedance, and yields from about xc2xd to 1 ampere when stopped and connected to a track voltage of about 12 Volts, typically used by a programmer. If the unpowered, or unoperated, Relay State connects the motor to the programming-track energy source, the locomotive installation presents an excessive power load to the programming-track; defined by the RP-9.2.3 as current greater than 0.25 Amperes after power on. Since the motor load is also typically used to signal programming success, or current pulse acknowledgement, and will often cause a collapse of the programming-track voltage due to required overcurrent fault protection, the premature and permanent operation of the motor will defeat reliable programming on necessarily power-limited programming-tracks specified by the NMRA RP-9.2.3.
If the relay unpowered state does not connect the motor to the track, then on a conventional track accurate mode-conversion is not possible since the relay cannot be operated until the track voltage raises sufficiently for the decoder control logic to work and then operate the relay. Ironically this is the exact problem the changeover switch method was intended to fix.
Graf fails to identify the existence of this major RP-9.2.3 programming problem when using a relay switch mechanism or to teach how this may be overcome. Additionally Graf fails to teach how the relay is energized and the logic by which it is controlled.
The prior art citations of mode-conversion technology, operating methods and decoder and DCC product design strategies presented are illustrative of the art and are considered incorporated herein by reference. In particular, the drawings of Graf depict a typical low-end decoder design with configurations of circuitry, or close functional derivatives, commonly found in many types of decoders.
The lowest cost switches, miniature DIP switches and miniature Reed relays suitable for the required motor current switching for voltage accurate mode-conversion, are configured as simple make-break (reed relay xe2x80x9cform Axe2x80x9d) contact units, and not the more complex and expensive changeover (reed relay xe2x80x9cform Cxe2x80x9d) contact styles that are required for the prior art.
An invention that allows the (voltage) accurate mode-conversion of a DCC equipped locomotive using simpler and less expensive make-break types of switches, and that can operate on a power-limited programming-track is a valuable addition to an improvement over the prior art of model railroad control.
Since 1997 Digitrax Inc. has produced DCC decoders with the unique ability to test the state of the motor isolation from the track connections at initial power-on. This is a novel fault detection method that finds and protects against the most common reason that decoder installations fail. This is the failure by the installer to remove the original locomotive motor to track connections from both of the motor leads correctly and hence allow the motor to powered solely by the decoder H-bridge output circuit. If any failure of isolation is detected, the Digitrax decoder will disable the H-bridge output circuit from driving the motor and no damage can occur to the H-bridge or decoder, since it will not be able to conflict with the track energy source, even though the decoder and H-bridge are also being powered by the track energy. It is also possible for the decoder to signal this measured and assumed fault state by blinking lights in a distinctive manner.
This protection method is very useful in allowing for a new and innovative way of forcing an accurate mode-conversion capability on the decoder. Since the motor leads may be selectively connected by simple jumpers to both the track and the decoder H-bridge output connections at the same time, without damaging the decoder, it is possible to use this direct metallic jumper connection to allow the motor to run accurately on conventional track power or energy. Since the decoder actively detects this state and responds in a safe and suitable manner, no ill effects will occur when the track power is also simultaneously jumper-connected to the motor in this manner, and the normal higher startup voltage of the decoder will not affect the accuracy of the motor speed operation. The unpowered state of the decoder and H-bridge is designed to be nonconductive to the motor output terminals. When the conventional track power is sufficient for the decoder to begin operation, the motor will typically already be in motion and the decoder will detect the track-motor jumpers and decline to operate the H-bridge output.
The decoder then knows that the motor is intended to run directly from track power and can analyze the track voltage encoding to provide any sensible possible supplementary control actions.
When operating in this state the decoder can still analyze the track voltage waveform to infer conventional operating direction, speed etc., and so can still operate other non-motor features such as; directional lights, FX lighting effect functions and any other capabilities such as data feedback of input lines, distance or location localizing Transponding, as taught in U.S. Pat. No. 6,220,552. Sound capable decoders can operate sound generation when the voltage is sufficient, and can even generate an alarm sound indication if the detected mode and track voltage is calculated to possibly permit damage to the motor. Sound synchronization cams and speed-varied sound are still operable by the decoder measuring the track voltages or timing cam inputs.
This new configuration disclosed herein is distinctly different to that of Kosinski, NMRA RP-9.1.1 and Graf, in that the decoder is definitely powered simultaneously to the motor and the decoder H-bridge output circuit is also always connected to the motor leads, irrespective of whether or not the track energy is also connected to the motor. This new configuration only needs two simple and inexpensive make-break jumpers or switch connections, and only four connection points are used to switch the currents, unlike the 6 connection points per switch of the double-pole changeover types of arrangements used in the prior art. This minimizes; the number of current carrying terminals, wire connections needed, Printed Circuit Board connection area and also improves reliability. This also allows the use of lower cost make-break or single throw type standard DIP switches or xe2x80x9cform Axe2x80x9d reed relays to effect the conversion.
This invention is not intended to be solely limited to DCC encoding format decoders, and may be employed in any type of decoder or receiver used for model layout control purposes by those skilled in the art of electronic circuit and control software design using the methods presented herein.